Darth Maul was more than likely younger than Vader, and he wasn't wearing a giant suit either. at any rate, Vader was a much more powerful sith than Maul, since he was able to exterminate almost the entire Jedi race.

__________________I know what you're thinking punk. You're thinking: "Did he fire six shots or only five?" Well, to tell you the truth, I've forgotten myself in all this excitement. But being as this is a .44 Magnum, the most powerful handgun in the world, and would blow your head clean off, you've got to ask yourself a question: "Do I feel lucky?" Well, do ya punk?

__________________I know what you're thinking punk. You're thinking: "Did he fire six shots or only five?" Well, to tell you the truth, I've forgotten myself in all this excitement. But being as this is a .44 Magnum, the most powerful handgun in the world, and would blow your head clean off, you've got to ask yourself a question: "Do I feel lucky?" Well, do ya punk?

according to the episode I DVD commentary, Vader was slow because his bionics hindered him. also, obi-wan was slow and out of practice, and Vader never meant to kill Luke.
Vader would win in the end because of his power in the force. According to current rumors, episode III will showcase Vader's true powers.

__________________Land of the free, home of the brave...
Do you think we will ever be saved?
In this land of dreams find myself sober...
Wonder when will it'll all be over...
Living in a void when the void grows colder...
Wonder when it'll all be over?
Will you be laughing when it's over?

Yoda would get his ass handed to him. Think about it. The main reason the Vader fights are slow is because we didn't have CGI back then. Vader has enough power over the force to compensate for his mechanical body. He would destroy Yoda, I mean Yoda even knew this, which is why he left. He couldn't defeat either Sidious or Vader.
I wouldn't be surprised if Lucas used CGI to redo that fight. Bot Obi-Wan and Vader deserve more credit. Look at Dooku, he's 80+ and he's doing flips in battle. Vader could as well.

__________________"The ability to destroy a planet is insignificant, next to the power of the force."

Uh he has, in the second Movie.
I would Bet on Vader though, He is just so much stronger than Yoda in a true lightsaber Clash, but if It came to battle of Force power, youda would own. Vader couldn't throw crap at Yoda, It would come flying back at him.